WO2016075942A1 - Dynamic quantity sensor - Google Patents

Abstract

A dynamic quantity sensor comprising a fixed part (20) fixed to a substrate (11), a floating part (30) supported on the fixed part, a detecting piezoelectric part (42a-42d) that converts strain in the floating part into electrical signals, a detecting pad (62a-62f) formed on the fixed part, and a plurality of detecting wires (72) that connect the detecting piezoelectric part with the detecting pad. The detecting piezoelectric part comprises a lower electrode (43), a piezoelectric material (44) and an upper electrode (45), laminated onto an insulation film (14) on the floating part. A portion of the detecting wires extends from the lower electrode, and the remainder is connected with a first connection site (46) which extends from the upper electrode along the side surface of the piezoelectric material to the insulation film-side and which is composed of the same material as the upper electrode. The detecting wires are provided on the insulation film and are composed of the same material as the lower electrode, the material having a yield stress of 70-800 MPa.

Description

Mechanical quantity sensor Cross-reference of related applications

This application is based on Japanese Patent Application No. 2014-230772 filed on November 13, 2014, the contents of which are incorporated herein by reference.

The present disclosure relates to a mechanical quantity sensor that converts strain generated by application of inertial force into an electric signal.

As shown in Patent Document 1, an angular velocity sensor element in which an internal drive unit, an external drive unit, and a detection unit are formed on a vibrating body is known. The vibrating body has two arms and a connecting portion that connects one end of each of the two arms. An internal drive unit, an external drive unit, and a detection unit are formed in each of the two arms, and the two arms are vibrated in opposite phases by the internal drive unit and the external drive unit. When an angular velocity is applied in a direction perpendicular to the vibration direction, a Coriolis force is generated in the arm, which causes distortion in the arm. This distortion is converted into an electric signal by the detection unit.

As described above, in the angular velocity sensor element disclosed in Patent Document 1, an internal drive unit, an external drive unit, and a detection unit are formed on the arm. The detection unit is divided into a detection region for detecting the distortion generated in the arm due to the Coriolis force and a wiring region for transmitting an electric signal detected in the detection region to an external processing circuit. Yes. The detection region and the wiring region have the same structure, and have a detection lower electrode, a detection piezoelectric thin film, and a detection upper electrode that are sequentially stacked on the arm. Therefore, when the arm is distorted by the Coriolis force described above, an electric signal (charge) corresponding to the distortion is generated not only in the detection region but also in the wiring region, which may reduce the angular velocity detection accuracy. In particular, in Patent Document 1, since the wiring region is located between the internal drive unit and the external drive unit, distortion due to vibrations of the internal drive unit and the external drive unit is more likely to occur in the wiring region than in the detection region. Therefore, a charge corresponding to the distortion caused by the vibration is also generated in the wiring region, and there is a possibility that the detection accuracy of the angular velocity is further lowered by this charge.

JP 2010-249713 A

This disclosure is intended to provide a mechanical quantity sensor in which a decrease in accuracy of detecting inertial force as angular velocity is suppressed.

In the first aspect of the present disclosure, the mechanical quantity sensor includes a fixed portion fixed to the upper surface of the substrate, a floating portion positioned above the substrate and supported by the fixed portion, and the inertial force applied by the inertial force sensor. A detection piezoelectric part that converts the distortion of the floating part into an electric signal, a detection pad formed on the fixed part, and a plurality of detection wirings that electrically connect the detection piezoelectric part and the detection pad And having. An insulating film is formed on the upper surface of the floating portion. The detection piezoelectric portion includes a lower electrode, a piezoelectric material, and an upper electrode that are sequentially stacked on the insulating film. A part of the plurality of detection wires extends from the lower electrode. The remainder of the plurality of detection wirings is electrically connected to a first connection portion made of the same material as the upper electrode extending from the upper electrode along the side surface of the piezoelectric material to the insulating film side. ing. The plurality of detection wirings are provided on the insulating film and are made of the same material as the lower electrode. The yield stress of the lower electrode forming material is 70 MPa to 800 MPa.

As described above, the detection wiring for connecting the detection piezoelectric portion and the detection pad is provided on the insulating film of the floating portion. The detection wiring is made of the same material as the lower electrode. According to this, even if the floating portion is distorted by the application of inertia force, unlike the configuration in which the detection wiring has the same structure as the detection piezoelectric portion, no charge is generated in the detection wiring. Therefore, a decrease in inertial force detection accuracy is suppressed as compared with the comparative configuration.

Since the detection wiring is made of the same material as that of the lower electrode as described above, the degree of adhesion between the detection wiring and the insulating film and the lower electrode are different from the configuration in which the detection wiring is made of a material different from that of the lower electrode. And the insulating film become equal in degree of adhesion. Therefore, even though the lower electrode and the insulating film are in close contact with each other, peeling of the detection wiring from the insulating film is suppressed. Furthermore, since the yield stress of the material for forming the lower electrode is 70 MPa to 800 MPa, even if the floating portion vibrates, the vibration suppresses the lower electrode and the detection wiring from being separated from the insulating film. Thereby, the lifetime reduction of the mechanical quantity sensor is suppressed.

As an alternative, the upper electrode and the lower electrode of the detection piezoelectric part may be made of different materials. The lower electrode is made of a material having higher adhesion to the insulating film than the upper electrode. According to this, unlike the structure in which the lower electrode is made of a material having lower adhesion to the insulating film than the upper electrode, the detection wiring is suppressed from being peeled off from the insulating film. Thereby, the lifetime reduction of the mechanical quantity sensor is suppressed.

The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. The drawing
FIG. 1 is a top view illustrating a schematic configuration of a mechanical quantity sensor according to the first embodiment. FIG. 2 is a sectional view taken along line II-II in FIG. FIG. 3 is an enlarged top view of a region A surrounded by a broken line in FIG. FIG. 4 is a sectional view taken along line IV-IV in FIG. FIG. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is an enlarged top view of a region B surrounded by a broken line in FIG. FIG. 7 is a conceptual diagram for explaining the vibration state of the mechanical quantity sensor. FIG. 8 is a conceptual diagram for explaining the vibration state of the mechanical quantity sensor. FIG. 9 is a conceptual diagram for explaining a state in which an angular velocity is applied to the mechanical sensor in the vibration state shown in FIG. FIG. 10 is a cross-sectional view showing a wiring configuration of the mechanical quantity sensor according to the second embodiment. FIG. 11 is a top view for explaining the wiring structure of the driving piezoelectric portion according to the second embodiment. 12 is a cross-sectional view taken along line XII-XII in FIG. 13 is a cross-sectional view taken along line XIII-XIII in FIG. FIG. 14 is a top view for explaining the detecting piezoelectric portion according to the second embodiment. FIG. 15 is a conceptual diagram for explaining the vibration state of the mechanical quantity sensor according to the third embodiment. FIG. 16 is a conceptual diagram for explaining the vibration state of the mechanical quantity sensor according to the third embodiment. FIG. 17 is a conceptual diagram for explaining a state in which an angular velocity is applied to the mechanical sensor in the vibration state shown in FIG. FIG. 18 is an enlarged top view for explaining a connection configuration of the driving piezoelectric portion shown in FIGS. FIG. 19 is an enlarged top view for explaining the slit formed in the fixed portion, 20 is a cross-sectional view taken along line XX-XX in FIG.

Hereinafter, an embodiment in which a mechanical quantity sensor according to the present disclosure is applied to an angular velocity sensor will be described with reference to the drawings.
(First embodiment)
A mechanical quantity sensor according to this embodiment will be described with reference to FIGS. 3 and 6, for the sake of clarity, the outlines of the constituent members that are not exposed to the outside are indicated by broken lines, and the connecting portions 46 described later are indicated by hatching. 7 to 9 show only the symbols necessary for explaining the detection of vibration and angular velocity in order to clearly show the vibration state of the mechanical quantity sensor.

In the following, three directions that are orthogonal to each other are indicated as an x direction, a y direction, and a z direction. A plane defined by the x direction and the y direction is an xy plane, a plane defined by the y direction and the z direction is a yz plane, and a plane defined by the z direction and the x direction is zx. Shown as a plane.

A mechanical quantity sensor 100 shown in FIG. 1 is a micro electromechanical (MEMS) formed by etching so as to form a fine structure on the SOI substrate 10. As shown in FIG. 2, the SOI substrate 10 includes a first substrate 11, a second substrate 12 positioned above the first substrate 11, and an insulating layer that mechanically connects the first substrate 11 and the second substrate 12. 13. The substrates 11 and 12 are each made of silicon, and the insulating layer 13 is made of silicon oxide. The second substrate 12 and the insulating layer 13 are etched into a predetermined shape, whereby the fixing portion 20 fixed to the first substrate 11 via the insulating layer 13 and the first substrate without the insulating layer 13 being interposed. The floating part 30 located on 11 is formed. The fixed portion 20 is immovable with respect to the first substrate 11, and the floating portion 30 is movable with respect to the first substrate 11, and each is formed by the second substrate 12.

1 and 2, the fixing portion 20 has a rectangular shape in the xy plane, and the insulating layer 13 is connected to the lower surface of the central portion 21 indicated by a broken line. An annular edge 22 that is located outside the central portion 21 and is not connected to the insulating layer 13 is continuously connected to the floating portion 30.

The floating part 30 has a frame part 31 and a support beam 32. As shown in FIG. 1, the frame portion 31 has an annular shape in the xy plane, and the fixing portion 20 is located in a region surrounded by the inner ring surface of the frame portion 31. The support beam 32 extends from the inner ring surface of the frame portion 31 toward the side surface of the fixed portion 20 and functions to mechanically connect the both.

The frame portion 31 has a rectangular ring shape in the xy plane, and includes two drive beams 33 having a shape extending in the x direction and two connecting beams 34 having a shape extending in the y direction. A mass part 35 having a locally wide width in the y direction is formed in each central part of the two drive beams 33, and the two mass parts 35 are arranged along the y direction via the fixing part 20. As will be described later, when the frame portion 31 vibrates, the two mass portions 35 mainly vibrate, and when an angular velocity is applied, a Coriolis force is generated in these.

The support beam 32 has a shape extending in the x direction, and the two support beams 32 are connected to the fixed portion 20 and the frame portion 31. As shown in FIG. 1, one support beam 32 is connected to one connection beam 34, and the two support beams 32 are arranged in the x direction via the fixing portion 20. As described above, when the Coriolis force is generated in the mass portion 35, the support beam 32 is distorted. Therefore, the angular velocity can be detected by detecting this distortion.

Hereinafter, in order to clarify the configuration, one of the two driving beams 33 is referred to as a first driving beam 33a and the other is referred to as a second driving beam 33b. The mass portion 35 formed on the first drive beam 33a is referred to as a first mass portion 35a, and the mass portion 35 formed on the second drive beam 33b is referred to as a second mass portion 35b. One of the two support beams 32 is a first support beam 32a, the other is a second support beam 32b, one of the two connection beams 34 is a first connection beam 34a, and the other is a second connection beam 34b. . The same applies to the drawings.

The piezoelectric part 40, the pad 60, and the wiring 70 are formed in the fixed part 20 and the floating part 30 shown above. The insulating film 14 shown in FIG. 2 is formed on the upper surface of each of the fixed portion 20 and the floating portion 30, and the piezoelectric portion 40, the pad 60, and the wiring 70 are formed on the insulating film 14. The insulating film 14 is silicon oxide or alumina.

The piezoelectric unit 40 includes a driving piezoelectric unit 41 and a detecting piezoelectric unit 42. As shown in FIGS. 3 to 6, the driving piezoelectric portion 41 and the detecting piezoelectric portion 42 have the same configuration, and the lower electrode 43, the piezoelectric material 44, and the upper electrode sequentially stacked on the insulating film 14, respectively. 45. The electric axis indicating the polarization direction of the piezoelectric material 44 is directed from the upper electrode 45 to the lower electrode 43 along the z direction. Therefore, the piezoelectric material 44 expands when the upper electrode 45 has a higher potential than the lower electrode 43, and the piezoelectric material 44 contracts when the lower electrode 43 has a higher potential than the upper electrode 45. When the piezoelectric material 44 extends due to distortion, a current flows from the upper electrode 45 to the lower electrode 43, and when the piezoelectric material 44 contracts, a current flows from the lower electrode 43 to the upper electrode 45. As the piezoelectric material 44 having such properties, for example, a PZT film or a ScAlN film can be employed. As shown in FIG. 1, each of the electrodes 43 and 45 and the piezoelectric material 44 has a shape extending in the x direction. Therefore, the expansion and contraction of the piezoelectric material 44 is increased in the x direction.

In this embodiment, the lower electrode 43 and the upper electrode 45 are made of different conductive materials, and the lower electrode 43 is made of a material having higher adhesion to the insulating film 14 than the upper electrode 45. In other words, the lower electrode 43 is made of a material having a higher yield stress than the upper electrode 45. As described above, the frame portion 31 vibrates, but the lower electrode 43 located on the frame portion 31 is deformed by the vibration. Therefore, if the yield stress of the lower electrode 43 is low, an irreversible change occurs during the above deformation, and even if the frame portion 31 tries to return to its original state, the lower electrode 43 does not return to its original state. There is a risk of peeling.

Al (aluminum) can be considered as the conductive material formed on the semiconductor substrate, but the yield stress of Al is about 15 MPa. The vibration frequency of the frame portion 31 is 4 to 50 kHz as will be described later. When the frame portion 31 vibrates in this way, when Al is used as the material of the lower electrode 43, the material for forming the lower electrode 43 is changed from the insulating film 14. It has been confirmed by the present inventors that it peels off. Therefore, a material higher than the yield stress of Al is adopted as a material for forming the lower electrode 43. As such a material, for example, Au (gold) or platinum (Pt) can be employed. The yield stress of Au is about 100 MPa, and the yield stress of Pt is about 70 MPa. Further, not only a single-layer conductive material but also a two-layer conductive material in which Au or Pt is laminated on Ti (titanium), for example, can be employed. In particular, SRO (strontium oxide) can be used as the upper electrode 45, and an SRO laminated on Pt can be used as the lower electrode 43. The yield stress of Ti and SRO is about 800 MPa. When the material having a yield stress of 70 MPa to 800 MPa as described above is used as the material for forming the lower electrode 43, the material for forming the lower electrode 43 is peeled off from the insulating film 14 even if the frame 31 vibrates as described above. The inventor has confirmed that this is difficult.

As shown in FIG. 1, the driving piezoelectric portion 41 is provided on the frame portion 31, and the detecting piezoelectric portion 42 is provided on the support beam 32. The frame portion 31 is vibrated by the driving piezoelectric portion 41, and the distortion of the support beam 32 caused by the application of the Coriolis force to the mass portion 35 is detected by the detecting piezoelectric portion 42.

The piezoelectric part 40 of this embodiment has eight driving piezoelectric parts 41 and four detecting piezoelectric parts 42. In the following, in order to clarify the difference between the eight driving piezoelectric portions 41 and the four detecting piezoelectric portions 42, the first driving piezoelectric portion 41a to the eighth driving piezoelectric portion 41h, the first detection piezoelectric portion 41, Piezoelectric portion 42a to fourth detecting piezoelectric portion 42d. The same applies to the drawings.

As shown in FIG. 1, two drive piezoelectric portions 41a and 41b are provided at one end of the first drive beam 33a, and two drive piezoelectric portions 41c and 41d are provided at the other end of the first drive beam 33a. . The driving piezoelectric portions 41a and 41c are located farther from the fixed portion 20 than the driving piezoelectric portions 41b and 41d, respectively. The driving piezoelectric portions 41a and 41b are electrically connected to each other in the y direction, and the driving piezoelectric portions 41c and 41d are electrically connected to each other in the y direction.

Similarly, two driving piezoelectric portions 41e and 41f are provided at one end of the second driving beam 33b, and two driving piezoelectric portions 41g and 41h are provided at the other end of the second driving beam 33b. The driving piezoelectric portions 41e and 41g are located farther from the fixed portion 20 than the driving piezoelectric portions 41f and 41h, respectively. The driving piezoelectric portions 41e and 41f are electrically connected to each other in the y direction, and the driving piezoelectric portions 41g and 41h are electrically connected to each other in the y direction.

As shown in FIG. 1, the two detection piezoelectric portions 42a and 42b are provided on the first support beam 32a, and the two detection piezoelectric portions 42c and 42d are provided on the second support beam 32b. Each of the detection piezoelectric portions 42a and 42c is positioned closer to the first mass portion 35a than each of the detection piezoelectric portions 42b and 42d, and each of the detection piezoelectric portions 42b and 42d is second than each of the detection piezoelectric portions 42a and 42c. It is located on the mass part 35b side.

The pad 60 has a driving pad 61 and a detection pad 62, which are formed in the fixed portion 20. As shown in FIG. 2, the driving pad 61 and the detection pad 62 have the same configuration, and each includes a first wiring layer 63 and a second wiring layer 64 that are sequentially stacked on the insulating film 14. The first wiring layer 63 is made of the same material as the lower electrode 43 and corresponds to the end of the wiring 70. The second wiring layer 64 is for increasing the rigidity of the pads 61 and 62, and for example, Al can be adopted. By the second wiring layer 64, damage to the pads 61 and 62 due to stress when connecting the wires to the pads 61 and 62 is suppressed.

As shown in FIG. 1, the pad 60 has three driving pads 61 and six detection pads 62. These pads 61 and 62 are arranged in a matrix so as to form 3 rows and 3 columns in the xy plane. Three drive pads 61 are arranged in the second row, and three detections are performed in the first and third rows, respectively. Pads 62 are lined up. As shown in FIG. 1, the driving pad 61 is located at the center portion 21 of the fixing portion 20, and the detection pad 62 is located at the edge portion 22 of the fixing portion 20. In the following, the three driving pads 61 arranged from the first row to the third row are referred to as a first driving pad 61a to a third driving pad 61c. In the first row, three detection pads 62 arranged from the first column to the third column are arranged as the first detection pad 62a to the third detection pad 62c, and in the third row, the first to third columns. The three detection pads 62 lined up toward are indicated as a fourth detection pad 62d to a sixth detection pad 62f. The same applies to the drawings. The mechanical quantity sensor 100 has a symmetric shape through the first center line passing through the center of the second driving pad 61b located in the second row and second column in the x direction and the second center line passing through the y direction. It is made.

As shown in FIG. 1, the second driving pad 61b is electrically connected to each of the eight driving piezoelectric portions 41a to 41h. The first driving pad 61a is electrically connected to the driving piezoelectric portions 41a and 41g, and the third driving pad 61c is electrically connected to the driving piezoelectric portions 41c and 41e. A constant voltage is input as a drive signal to the second drive pad 61b, and an in-phase pulse signal is input as the drive signal to the remaining two drive pads 61a and 61c. The pulse period of this pulse signal is set based on the resonance frequency of the frame portion 31 and is 20 kHz in this embodiment. Due to the input of the drive signal, the drive piezoelectric portions 41a to 41h expand and contract, and the frame portion 31 ( mass portions 35a and 35b) vibrates at a frequency of 4 to 50 kHz and an amplitude of 1 to 50 μm. The reason why the frequency and amplitude of the frame 31 have a width despite the pulse period being fixed at 20 kHz is that the Q value changes due to the mass and size of the frame 31. .

Further, as shown in FIG. 1, the second detection pad 62b located in the middle of the first row is electrically connected to each of the two detection piezoelectric portions 42a and 42c. The first detection pad 62a is electrically connected to the first detection piezoelectric portion 42a, and the third detection pad 62c is electrically connected to the third detection piezoelectric portion 42c. The second detection pad 62b is connected to the ground, and an electric signal corresponding to the distortion of the support beams 32a and 32b is input to the remaining two detection pads 62a and 62c. In the present embodiment, the second detection pad 62b is connected to the lower electrode 43 of each of the detection piezoelectric portions 42a and 42c. The first detection pad 62a is connected to the upper electrode 45 of the first detection piezoelectric portion 42a, and the third detection pad 62c is connected to the upper electrode 45 of the third detection piezoelectric portion 42c. The connection relationship between the electrodes 43 and 45 and the detection pads 62a to 62c may be reversed.

Similarly, the fifth detection pad 62e located in the middle of the third row is electrically connected to each of the two detection piezoelectric portions 42b and 42d. The fourth detection pad 62d is electrically connected to the second detection piezoelectric portion 42b, and the sixth detection pad 62f is electrically connected to the fourth detection piezoelectric portion 42d. The fifth detection pad 62e is connected to the ground, and an electric signal corresponding to the distortion of the support beams 32a and 32b is input to the remaining two detection pads 62d and 62f. In the present embodiment, the fifth detection pad 62e is connected to the lower electrode 43 of each of the detection piezoelectric portions 42b and 42d. The fourth detection pad 62d is connected to the upper electrode 45 of the second detection piezoelectric portion 42b, and the sixth detection pad 62f is connected to the upper electrode 45 of the fourth detection piezoelectric portion 42d. The connection relationship between the electrodes 43 and 45 and the detection pads 62d to 62f may be reversed.

The wiring 70 electrically connects the piezoelectric part 40 and the pad 60 and is made of the same material as the lower electrode 43 constituting the piezoelectric part 40. Therefore, the degree of adhesion between the wiring 70 and the insulating film 14 is equal to that of the lower electrode 43. The wiring 70 includes a driving wiring 71 that electrically connects the driving piezoelectric portion 41 and the driving pad 61, and a detection wiring 72 that electrically connects the detecting piezoelectric portion 42 and the detection pad 62. Have. As shown in FIGS. 3 to 5, the end of the driving wiring 71 connected to the lower electrode 43 extends from the lower electrode 43, and the end connected to the upper electrode 45 extends from the upper electrode 45 to the piezoelectric material 44. It is electrically connected to a connecting portion 46 extending to the insulating film 14 side through the side surface. As shown in FIG. 6, the detection wiring 72 has the same configuration. As shown in FIGS. 1 and 2, the ends of the wirings 71 and 72 that are electrically connected to the pads 60 are extended from the first wiring layer 63 of the pads 61 and 62.

Next, a method for forming the piezoelectric portions 41 and 42, the pads 61 and 62, and the wirings 71 and 72 will be briefly described. As described above, the first wiring layer 63 and the wirings 71 and 72 of the pads 61 and 62 are made of the same material as the lower electrode 43 of the piezoelectric parts 41 and 42, respectively. Therefore, a material for forming the lower electrode 43 (hereinafter referred to as a lower material) is laminated on the insulating film 14, and then the first wiring layer 63, the wirings 71 and 72, and the lower electrode 43 are formed thereon. A resist is formed. Then, the lower material exposed to the outside from the resist is removed by etching. Thus, the first wiring layer 63, the wirings 71 and 72, and the lower electrode 43 are formed. Next, the piezoelectric material 44 is laminated on the lower material constituting the lower electrode 43 and the ends of the wirings 71 and 72 electrically connected to the upper electrode 45. Thereafter, a material for forming the upper electrode 45 is formed at the ends of the piezoelectric material 44 and the wirings 71 and 72 on which the piezoelectric material 44 is laminated, and etched into a predetermined shape. By doing so, the upper electrode 45 and the connecting portion 46 are formed, and the upper electrode 45 and the wirings 71 and 72 are electrically connected. Finally, the second wiring layer 64 is formed on the first wiring layer 63 of the pads 61 and 62. Thus, the piezoelectric portions 41 and 42, the pads 61 and 62, and the wirings 71 and 72 are formed.

Next, a connection structure of two driving piezoelectric parts arranged in the y direction and electrically connected to each other is shown. There are a total of four of these two drive piezoelectric parts, but since these connection structures are the same, the connection structure of the drive piezoelectric parts 41c and 41d will be described with reference to FIGS. 3 to 5 and 43c to 45c and 43d to 45d are shown in order to distinguish the constituent materials 43 to 45 of the driving piezoelectric portions 41c and 41d.

As shown in FIGS. 3 and 4, a driving wiring 71 is extended from the lower electrode 43c of the third driving piezoelectric portion 41c, and the driving wiring 71 is electrically connected to the upper electrode 45d of the fourth driving piezoelectric portion 41d. It is connected to the. As shown in FIG. 1, the driving wiring 71 is connected to the second driving pad 61b. Therefore, each of the lower electrode 43c and the upper electrode 45d is fixed to the ground potential. Further, as shown in FIGS. 3 and 5, a driving wiring 71 is extended from the lower electrode 43d of the fourth driving piezoelectric portion 41d, and the driving wiring 71 is electrically connected to the upper electrode 45c of the third driving piezoelectric portion 41c. Connected. As shown in FIGS. 1 and 3, the upper electrode 45 c is connected to the third driving pad 61 c via the driving wiring 71. Therefore, a pulse signal having a pulse period determined based on the resonance frequency of the frame portion 31 is input to each of the upper electrode 45c and the lower electrode 43d. With the above connection configuration, the voltage applied to the driving piezoelectric portions 41c and 41d is reversed with respect to the electric axis. Therefore, when one of the driving piezoelectric portions 41c and 41d is extended by the input of the pulse signal, the other is contracted.

Next, the movement of the frame 31 will be described with reference to FIGS. As described above, when one of the driving piezoelectric portions 41c and 41d expands, the other contracts, but this relationship relates to the driving piezoelectric portions 41a and 41b, the driving piezoelectric portions 41e and 41f, and the driving piezoelectric portions 41g and 41h, respectively. Also holds. That is, when each of the driving piezoelectric portions 41a, 41c, 41e, and 41g located away from the fixed portion 20 extends, each of the driving piezoelectric portions 41b, 41d, 41f, and 41h positioned on the fixed portion 20 side contracts. On the other hand, when each of the driving piezoelectric portions 41a, 41c, 41e, and 41g contracts, each of the driving piezoelectric portions 41b, 41d, 41f, and 41h extends.

Therefore, as shown by the white arrow in FIG. 7, when a drive signal is input, a current that causes the drive piezoelectric portions 41a, 41c, 41e, and 41g to extend and the drive piezoelectric portions 41b, 41d, 41f, and 41h to contract flows. Each of the two mass parts 35 a and 35 b is displaced toward the fixed part 20. When the driving piezoelectric portions 41a, 41c, 41e, and 41g contract as shown by white arrows in FIG. 8 and the driving piezoelectric portions 41b, 41d, 41f, and 41h extend, two mass portions 35a, Each of 35b is displaced away from the fixing portion 20. As described above, the input of the drive signal causes the two mass portions 35a and 35b to vibrate so as to approach each other and move away from each other in the y direction.

Next, the Coriolis force generated when the angular velocity is applied to the mass portions 35a and 35b in the vibration state shown in FIG. 7 will be described with reference to FIG. As described above, when the two mass parts 35a and 35b vibrate so as to approach each other or move away from each other in the y direction, if an angular velocity along the z direction is applied, the two mass parts 35a and 35b are applied to the two mass parts 35a and 35b. The Coriolis force along the x direction is generated in the opposite direction. As a result, the frame portion 31 tends to rotate in the xy plane around an axis that penetrates the center of the fixed portion 20 (the center of the second driving pad 61b) in the z direction. The movement of the frame portion 31 causes distortion in the two support beams 32a and 32b, and distortion occurs in each of the detection piezoelectric portions 42a to 42d provided on the support beams 32a and 32b. As a result of the Coriolis force indicated by hatching arrows in FIG. 9 occurring in the mass portions 35a and 35b, when the frame portion 31 attempts to rotate clockwise, the first support beam 32a has a fulcrum at the end connected to the fixed portion 20. As a result, the end connected to the connecting beam 34 moves upward in the drawing. On the other hand, the second support beam 32b is moved downward in the drawing with the end connected to the fixed beam 20 as a fulcrum. As a result, as shown by hatching arrows in FIG. 9, distortion that contracts in the detection piezoelectric portions 42 a and 42 d occurs, and distortion that extends in the detection piezoelectric portions 42 b and 42 c occurs. As a result, reverse currents flow through the detection pads 62a and 62f connected to the detection piezoelectric portions 42a and 42d and the detection pads 62c and 62d connected to the detection piezoelectric portions 42b and 42c. The current flowing through the detection pads 62a, 62c, 62d, and 62f is output to an external device via a wire, and the angular velocity is detected by performing signal processing on the external device. Although not shown, when the frame portion 31 attempts to rotate counterclockwise, the end portion of the first support beam 32a connected to the connection beam 34 moves downward in the drawing, and the connection beam 34 of the second support beam 32b. The end part connected to is moved upward in the drawing. As a result, distortion that expands in the detection piezoelectric portions 42a and 42d occurs, and distortion that contracts in the detection piezoelectric portions 42b and 42c occurs.

Next, functions and effects of the mechanical quantity sensor 100 according to the present embodiment will be described. As described above, the wirings 71 and 72 are made of the same material as the lower electrode 43 and are provided on the insulating film 14 of the floating portion 30. According to this, even if the floating portion 30 is distorted by the application of inertial force, unlike the configuration in which the wiring has the same structure as the piezoelectric portion, no charges are generated in the wirings 71 and 72, respectively. Therefore, a decrease in angular velocity detection accuracy is suppressed as compared with the comparative configuration.

Particularly in this embodiment, the drive wiring 71 is provided on the insulating film 14 of the frame portion 31 that functions as a vibrating body. According to this, unlike the above-described comparative configuration, the generation of charges in the drive wiring 71 due to the vibration of the frame portion 31 is suppressed, and the drive piezoelectric portion 41 is expanded and contracted by the generated charges. It is suppressed that the vibration state of the part 31 becomes unstable. This suppresses a decrease in angular velocity detection accuracy.

Further, as described above, since the wirings 71 and 72 are made of the same material as that of the lower electrode 43, the degree of adhesion between the wirings 71 and 72 and the insulating film 14 is different from the structure in which the wiring is made of a material different from that of the lower electrode. The degree of adhesion between the lower electrode 43 and the insulating film 14 becomes equal. Accordingly, it is possible to suppress the wirings 71 and 72 from being separated from the insulating film 14 even though the lower electrode 43 and the insulating film 14 are in close contact with each other. Furthermore, since the yield stress of the material for forming the lower electrode 43 is 70 MPa to 800 MPa, the lower electrode 43 and the wirings 71 and 72 are prevented from being separated from the insulating film 14 due to the vibration of the floating portion 30. Thereby, the lifetime reduction of the mechanical quantity sensor 100 is suppressed.

Furthermore, in this embodiment, the lower electrode 43 is made of a material having higher adhesion to the insulating film 14 than the upper electrode 45. According to this, unlike the structure in which the lower electrode is made of a material having lower adhesion to the insulating film than the upper electrode, the wirings 71 and 72 are suppressed from being peeled off from the insulating film 14. Thereby, the lifetime reduction of the mechanical quantity sensor 100 is suppressed.

(Second Embodiment)
Next, a second embodiment of the present disclosure will be described based on FIGS. 10 to 14. The mechanical quantity sensor according to the second embodiment has much in common with the above-described embodiment. Therefore, in the following description, description of common parts is omitted, and different parts are mainly described. In the following description, the same reference numerals are given to the same elements as those described in the above embodiment.

In the first embodiment, an example in which the lower electrode 43 and the upper electrode 45 are made of different conductive materials is shown. In contrast, the present embodiment is characterized in that the lower electrode 43 and the upper electrode 45 are made of the same conductive material.

In this case, the etching rate of the material for forming the lower electrode 43 and the material for forming the upper electrode 45 are the same. Therefore, in order to avoid etching the forming material of the lower electrode 43 when the forming material of the upper electrode 45 is etched, the forming material of the lower electrode 43 depends on the forming material of the upper electrode 45 as shown in FIGS. Covered. For example, as shown in FIG. 10, the wirings 71 and 72 and the first wiring layer 63 of the pads 61 and 62 are each made of the forming material of the electrodes 43 and 45, and these two forming materials are provided on the insulating film 14. . As a result, the connection area between the wirings 71 and 72 and the respective insulating films 14 of the first wiring layer 63 is increased as compared with the configuration shown in the first embodiment, and the wirings 71 and 72 and the first wiring layer 63 are insulated. Peeling from the film 14 is suppressed.

As shown in FIGS. 11 and 12, the driving wiring 71 that electrically connects the lower electrode 43c and the upper electrode 45d has a portion extending from the lower electrode 43c depending on a portion extending from the upper electrode 45d. Consists of. Further, as shown in FIGS. 11 and 13, in the driving wiring 71 that electrically connects the lower electrode 43d and the upper electrode 45c, a portion extending from the lower electrode 43d is a portion extending from the upper electrode 45c. Covered by. The drive wiring 71 that electrically connects the upper electrode 45c and the third drive pad 61c is covered with a portion where the material for forming the lower electrode 43 extends from the upper electrode 45c. Further, as shown in FIG. 14, the detection wiring 72 that electrically connects the lower electrode 43 of the first detection piezoelectric portion 42a and the second detection pad 62b is connected to the lower electrode 43 of the first detection piezoelectric portion 42a. The extended portion is covered with the material for forming the upper electrode 45.

The formation material of the electrodes 43 and 45 is the same as that of the first embodiment in order to prevent the electrode 43, the wirings 71 and 72, and the pads 61 and 62 from being separated from the insulating film 14 due to the vibration of the frame portion 31. A material having a higher yield stress than Al (a material having a yield stress of 70 MPa to 800 MPa) is employed. As such a material, as shown in the first embodiment, Au, Pt, and Ti laminated with Au or Pt, or Pt laminated with SRO can be adopted.

(Third embodiment)
Next, a third embodiment of the present disclosure will be described based on FIGS. 15 to 18. The mechanical quantity sensor according to the third embodiment has much in common with the above-described embodiment. Therefore, in the following description, description of common parts is omitted, and different parts are mainly described. In the following description, the same reference numerals are given to the same elements as those described in the above embodiment.

In the first embodiment, an example in which the two mass portions 35a and 35b vibrate so as to approach each other or move away from each other in the y direction has been described. On the other hand, the present embodiment is characterized in that in the z direction, one of the two mass portions 35a, 35b vibrates so as to approach the first substrate 11 and the other away from the first substrate 11.

In order to vibrate the mass portions 35a and 35b in the z direction as described above, as shown in FIG. 15, the driving piezoelectric portions 41a to 41d provided on the first driving beam 33a are extended and the second driving beam 33b is extended. Each of the driving piezoelectric portions 41e to 41h provided in the slidable portion is contracted. Then, as shown in FIG. 16, the driving piezoelectric portions 41a to 41d provided on the first driving beam 33a are contracted, and the driving piezoelectric portions 41e to 41h provided on the second driving beam 33b are extended. By extending and contracting the driving piezoelectric portions 41a to 41h in this way, vibration is performed so that one of the two mass portions 35a and 35b is closer to the first substrate 11 and the other is away from the first substrate 11 in the z direction. . When an angular velocity along the y direction is applied as shown in FIG. 17 in this vibration state, a Coriolis force along the x direction is generated in the opposite direction in the two mass portions 35a and 35b. As a result, the frame portion 31 tends to rotate in the xy plane around an axis penetrating the center of the fixed portion 20 in the z direction. Due to this rotation, distortion occurs in the two support beams 32, and currents corresponding to the distortion flow in the detection piezoelectric portions 42 a to 42 d provided on the support beams 32.

When the mass portions 35a and 35b are vibrated as shown in FIGS. 15 to 17, the connection structure of the driving piezoelectric portions 41a to 41h is different from that shown in the other embodiments. For example, as shown in FIG. 18, driving wires 71 extending from the lower electrodes 43c and 43d of the driving piezoelectric portions 41c and 41d are electrically connected to each other, and the driving wires 71 are connected to the second driving pads. 61b. Accordingly, each of the lower electrodes 43c and 43d is fixed to the ground potential. The upper electrodes 45c and 45d of the driving piezoelectric portions 41c and 41d are electrically connected via the driving wiring 71, and these are connected to the third driving pad 61c. Accordingly, a pulse signal having a pulse period determined based on the resonance frequency of the frame portion 31 is input to each of the upper electrodes 45c and 45d. With the above connection configuration, each of the driving piezoelectric portions 41c and 41d is similarly expanded and contracted by the input of the pulse signal.

As described above, a pulse signal is input to the upper electrodes 45 of the driving piezoelectric portions 41c and 41d, and the driving piezoelectric portions 41a and 41a provided on the first driving beam 33a in the same manner as the driving piezoelectric portions 41c and 41d. A pulse signal is also input to the upper electrode 45 of 41b. However, as described above, when each of the driving piezoelectric portions 41a to 41d provided on the first driving beam 33a is extended, each of the driving piezoelectric portions 41e to 41h provided on the second driving beam 33b is contracted. Therefore, a pulse signal is input to the lower electrode 43 of the driving piezoelectric portions 41e to 41h provided on the second driving beam 33b. As a result, the expansion and contraction directions of the driving piezoelectric portions 41a to 41d provided on the first driving beam 33a and the driving piezoelectric portions 41e to 41h provided on the second driving beam 33b are reversed, and the mass portions 35a, 35b vibrates in the z direction.

The preferred embodiments of the present disclosure have been described above. However, the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure.

In each embodiment, an example in which the mechanical quantity sensor 100 detects the angular velocity is shown. However, the mechanical quantity sensor 100 may detect acceleration. In this case, the driving piezoelectric portions 41a to 41h, the driving pads 61a to 61c, and the driving wiring 71 are not necessary. The acceleration detection direction is the y direction. When each of the mass portions 35a and 35b is displaced in the same direction in the y direction due to the inertial force caused by the acceleration applied in the y direction, the support beams 32a and 32b are distorted thereby. Current corresponding to the distortion is generated in the detection piezoelectric portions 42a to 42d.

Although not specifically described in each embodiment, for example, as shown in FIGS. 19 and 20, a central portion 21 of the fixing portion 20 in which the insulating layer 13 is connected to the lower surface and a fixing portion in which the insulating layer 13 is not connected to the lower surface. A slit 23 may be formed between the 20 edge portions 22. According to this, for example, stress due to deformation of the first substrate 11 is suppressed from being transmitted to the floating portion 30 via the edge portion 22 of the fixed portion 20. Therefore, a change in the vibration state of the frame portion 31 due to the vibration is suppressed, and distortion of the frame portion 31 is also suppressed. For this reason, it is suppressed that the detection accuracy of angular velocity falls. In particular, as shown in FIGS. 19 and 20, the slit 23 described above may extend in the x direction and be positioned between the drive pad 61 and the detection pad 62. According to this, the distortion generated in one of the driving pad 61 and the detection pad 62 is suppressed from being transmitted to the other.

In each embodiment, an example in which the electrical axis of the piezoelectric material 44 is directed from the upper electrode 45 toward the lower electrode 43 along the z direction is shown. However, the electric axis of the piezoelectric material 44 may be directed from the lower electrode 43 to the upper electrode 45 along the z direction.

In each embodiment, an example in which each of the pads 61 and 62 includes the first wiring layer 63 and the second wiring layer 64 is shown. However, each of the pads 61 and 62 may not have the second wiring layer 64. Moreover, although the example which employ | adopted Al as a forming material of the 2nd wiring layer 64 was shown, it is not limited to this, What is necessary is just for raising the rigidity of the pads 61 and 62. FIG.

In each embodiment, the pad 60 has three drive pads 61 and six detection pads 62, and the pads 61 and 62 are arranged in a matrix so as to form 3 rows and 3 columns. However, the number and arrangement of the pads 61 and 62 are not limited to the above example.

Although the present disclosure has been described based on the embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more or less, are within the scope and spirit of the present disclosure.

Claims (11)

1. A fixing part (20) fixed to the upper surface of the substrate (11);
   A floating part (30) located above the substrate and supported by the fixed part;
   A detecting piezoelectric part (42a to 42d) for converting the distortion of the floating part by application of inertial force into an electric signal;
   Detection pads (62a to 62f) formed on the fixed portion;
   A plurality of detection wirings (72) for electrically connecting the detection piezoelectric portion and the detection pad;
   An insulating film (14) is formed on the upper surface of the floating portion,
   The detection piezoelectric portion includes a lower electrode (43), a piezoelectric material (44), and an upper electrode (45) sequentially stacked on the insulating film,
   A part of the plurality of detection wires extends from the lower electrode,
   The remainder of the plurality of detection wirings is electrically connected to the first connection portion (46) made of the same material as the upper electrode extending from the upper electrode to the insulating film side through the side surface of the piezoelectric material. Connected to
   The plurality of detection wirings are provided on the insulating film and are made of the same material as the lower electrode,
   A mechanical quantity sensor in which a yield stress of a material for forming the lower electrode is 70 MPa to 800 MPa.
2. The upper electrode and the lower electrode of the detection piezoelectric portion are made of different materials,
   The mechanical sensor according to claim 1, wherein the lower electrode is made of a material having higher adhesion to the insulating film than the upper electrode.
3. The mechanical quantity sensor according to claim 1, wherein the upper electrode and the lower electrode of the detection piezoelectric portion are made of the same material.
4. The floating portion includes a frame portion (31) having a frame shape, and support beams (32a, 32b) that connect the frame portion and the fixed portion,
   The fixing portion is located in a region surrounded by the inner ring surface of the frame portion;
   The support beam has a shape extending from the inner ring surface of the frame portion toward the side surface of the fixed portion,
   The mechanical quantity sensor according to any one of claims 1 to 3, wherein the detection piezoelectric portion is provided on the support beam.
5. In addition to the detection pads, driving pads (61a to 61c) are formed on the fixed portion,
   A driving piezoelectric portion (41a to 41h) provided on the frame portion and vibrating the frame portion;
   A plurality of driving wirings (71) for electrically connecting the driving piezoelectric portion and the driving pad;
   The driving piezoelectric portion includes a lower electrode (43), a piezoelectric material (44), and an upper electrode (45) sequentially stacked on the insulating film,
   One end of each of the plurality of driving wirings (71) extends from the lower electrode of the driving piezoelectric portion and is electrically connected to the lower electrode of the detecting piezoelectric portion. Alternatively, the second connecting portion (46) made of the same material as the upper electrode of the detecting piezoelectric portion extends from the upper electrode of the driving piezoelectric portion to the insulating film side through the side surface of the piezoelectric material. Is electrically connected to
   The mechanical quantity sensor according to claim 4, wherein the plurality of drive wirings (71) are provided on the insulating film and are made of the same material as the lower electrode.
6. The upper electrode of the driving piezoelectric portion and the lower electrode of the driving piezoelectric portion are made of different materials,
   The mechanical quantity sensor according to claim 5, wherein the lower electrode of the driving piezoelectric portion is made of a material having higher adhesion to the insulating film than the upper electrode of the driving piezoelectric portion.
7. The mechanical quantity sensor according to claim 5, wherein the upper electrode of the driving piezoelectric portion and the lower electrode of the driving piezoelectric portion are made of the same material.
8. Two mass parts (35a, 35b) having a locally widened width are formed in the frame part,
   The two mass parts are arranged in the first direction along the upper surface of the substrate via the fixing part,
   The driving piezoelectric portion vibrates the frame portion so that the two mass portions approach each other or move away from each other in the first direction, or two piezoelectric portions in the second direction orthogonal to the upper surface of the substrate. The mechanical quantity sensor according to any one of claims 5 to 7, wherein the frame portion is vibrated so that one of the mass portions approaches the upper surface of the substrate and the other moves away from the upper surface of the substrate.
9. When the direction orthogonal to the first direction is the third direction along the upper surface of the substrate,
   The frame portion has a rectangular frame shape in a plane defined by the third direction and the first direction, and two drive beams (33a, 33b) having a shape extending in the third direction, And two connecting beams (34) having a shape extending in the first direction,
   One mass part is formed per one driving beam, and the two mass parts are arranged in the first direction via the fixing part,
   The floating portion has the two support beams,
   Each of the two support beams has a shape extending in the third direction,
   The mechanical quantity sensor according to claim 8, wherein one support beam is connected to one connection beam, and two support beams are connected in the third direction via the fixing portion.
10. 10. The mechanical quantity sensor according to claim 5, wherein a slit is formed between the detection pad and the driving pad in the fixed portion.
11. The fixing part is fixed to the substrate via an insulating layer (13),
    The mechanical quantity sensor according to claim 10, wherein the insulating layer is connected to a back surface of a region where the driving pad is formed on an upper surface of the fixing portion.
    

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